Unified Power Flow Controller Active Power Supply via HVDC Station
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Solution Overview
Problem
The increasing number of DC converter stations in HVDC projects in China poses a challenge in reducing the number of transformers and shunt converters at the parallel side of the Unified Power Flow Controller, necessitating a cost-effective and reliable method to provide active power for the AC side of the HVDC converter station.
Innovation Solution
A novel Unified Power Flow Controller is designed with a series converter, series transformer, DC converter, and control circuit, where the HVDC Converter Station supplies active power to the series converter, and internal capacitors provide reactive power, allowing operation in UPFC and SSSC modes by controlling DC switch blocks, reducing the need for transformers and shunt converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of transformers and shunt converters at the shunt side of UPFC is reduced, then operation costs are reduced and device complexity is reduced, but the ability to provide active power to the series converter becomes insufficient
Solution Approach 1:
The HVDC converter station is designed to perform multiple functions: it not only performs its traditional HVDC conversion function but also serves as an active power source for the UPFC series converter. The DC converter can operate in different modes to provide active power to the series converter when needed, while the internal capacitors of the series converter provide reactive power, eliminating the need for separate shunt converters and transformers.
2Device complexity
If the HVDC Converter Station is used to provide active power for the series converter, then operation costs are reduced and device complexity is reduced, but the reliability of power supply may be affected
Solution Approach 1:
The control circuit can dynamically adjust the operating parameters of the DC converter and series converter based on system conditions. By changing control laws and operating modes, the system can ensure reliable operation under different scenarios while maintaining the simplified configuration without traditional shunt converters and transformers.
3Device complexity
If internal capacitors are used to provide reactive power, then device complexity is reduced and operation costs are reduced, but the active power consumption of the series converter must be compensated
Solution Approach 1:
The patent combines the functions of active and reactive power compensation into a unified system. The DC converter provides active power compensation while the internal capacitors provide reactive power compensation, with both functions coordinated through a single control circuit. This merged approach eliminates the need for separate compensation devices and optimizes overall system efficiency.
Data Source
AI summary
The present invention discloses a novel Unified Power Flow Controller UPFC and its control method. Supposing that one end of DC converter is connected to the DC transmission line of HVDC converter station or substation and the other end is connected to the DC side of a series converter, the AC output voltage of the series converter can be controlled to regulate the line power of the UPFC for operation in UPFC and SSSC mode. In addition, when the number of transformers and shunt converters is decreased at the shunt side of the UPFC, the HVDC Converter Station can be used to provide active power for the series converter of UPFC, which can effectively reduce operation costs and ensure stable operation of power grid. Therefore, there is a bright application prospect for the invention.